Anneal steel in lead pot?

[lar45]

I have a breach section of an M1 Garand barrel that I was wanting to build into a something. The metal is very hard and I was haveing a hard time boreing it out to have a 1/2" hole all the way through to start with.
I fired up my Lee pot and put the barrel stub in the pot and turned the dial to the halfway mark and left it for a couple of hours. I pulled it out with pliers and wiped the lead off with a leather glove, then laid it on top to cool with the pot turned off. After it was all cooled down, I put it in the lathe and drilled my 1/2" hole all the way through without any problems.
I did a couple of grade 8 bolts at the same time.

Anybody else try this? Any problems with it that I'm not thinking about?

[ARKANSAS PACKRAT]

lar45; The only thing i'd suggest would be to put the metal into wood ashes to get a slower cool, some steels may not soften properly with air cooling. The even heat in the leadpot stops warping, air cooling might cause some warping from uneven cooling, not a problem with a heavy section but possible on lighter/slim pieces.
Sounds like a good way to get even heating on a part if it'll go in the pot!
I temper springs in oil and allow them to cool in the bath, gives the best even temper possible, no hard or soft spots.
Nick

[garandsrus]

Lar45,

A batch of Garand receivers (I don't remember the numbers or maker) were found to not be heat treated properly so they dipped them in molten lead to fix the problem. You can see a slightly different color in the receiver.

Here's some text about the problem that I found on another site:
The heels of some WWII era receivers were dipped in molten lead to anneal them to prevent them from cracking as the bolt slammed into the rear portion of the receiver during operation. This heating process leaves the area that was dipped in lead a darker color than the rest of the receiver. There is no residual lead there, but rather the steel will show a difference in color due to the heat treatment once it has been Parkerized. From my understanding, certain receivers made in 1943 were the main concern at that time however earlier and later receivers will also show the affects of annealing. So it was a preventative measure.

Here's a picture (not mine): http://s163.photobucket.com/albums/t297/kggarrett1911/?action=view&current=P1000181.jpg

I have a receiver that was dipped, but the difference in color is not as pronounced as this photo shows.

John

[grumpy one]

A minor nit-pick: you cannot anneal steel without heating it above 723*C (1333*F). What you do by heating to lesser temperatures is temper it. Tempered martensite can be machinable, though it remains rather tough compared with the same steel in the annealed condition. While tempering is mostly used to ameliorate the extreme brittleness of fully hard martensite, it can be a useful compromise when you don't want it fully softened, when you can't reach the required temperature, and when you want to avoid the degree of distortion likely to occur when you heat it above 723*C.

[KCSO]

I have used a led pot to temper sear and mainsprings on occasion and it works OK. Sounds like you found your fix.

[lar45]

Grumpy, thanks for the clarification. I paused on that when typeing, but couldn't remember clearly where it was at. Would you happen to know the bad heat regions for common firearms metals where temper imbrittlement happens? It seems like it is somewhere around 450-550 F and if the steel is kept at that temp for extended times it becomes very brittle. If it happens, can the piece be heated up to Austenite and quenched to start over without any problems?

For slow cooling, I've heard of burying the piece in sand. How does this compare to the wood ashes?

TIA

[grumpy one]

Hi Lar, I can't relate to your first question. Brittle steel after heat treatment is almost always a result of it consisting of untempered martensite, which is extremely brittle - in fact you are likely to get quench cracking if the design includes sharp corners. There is a sort of exception to this being the only common cause: - you can get hydrogen embrittlement from chrome plating martensitic steel. Tempering always softens the steel. It isn't normally practical to harden it again after tempering except by heating it back into the austenite zone above the A1-3 line.

With an alloy steel when you quench it too fast, you cut through one of the zones on the Time-Temperature-Transformation chart that you had intended to miss. Then you end up with more martensite than you had wanted in a heat treated alloy that was supposed to be only partly martensitic. So far as making something brittle by holding it at an elevated temperature is concerned, it doesn't ring any bells with me. However in any case, you can always undo a heat treatment by raising the steel article back above 723*C for a while, then quenching it and tempering it all over again.

The way to cool the article slower than air cooling (normalising) if you have a heat treatment works is usually to just switch off the furnace and let it cool overnight with the article inside it. For amateurs, sand or other refractory material is packed around the item while it is above 723*C. Ashes do not do the same job of holding heat - all they do is mess up convective movement of air, so they do not slow the cooling nearly as much as packing in sand would.

Geoff

[charger 1]

I cant see that true annealing happened in a lead melt situation. You wouldnt be getting hot enough. You MAY,and I emphasize MAY be getting warm enough for s tempering, but not an anneal

[leftiye]

Second Grumpy, and chargar about it not being hot enough for true annealing.

But unless my memory is off, molten lead is at the top end of tempering (should read drawing - you draw off the hardness of hardening to get temper) -temperatures or more likely quite a bit above tempering temperatures depending on the lead temperature. Therefore you are probably getting what should be called partial annealing. Once you go beyond the "spring" temper (blue oxide), then standard tempering is done, and behind you. I think this happens around 450 degrees, and soaking will push the effect stil further.